Field of the Invention
The present invention relates to a semiconductor pressure sensor and a method of fabricating the semiconductor pressure sensor, particularly a semiconductor pressure sensor including a MOS circuit, and a method of fabricating such a semiconductor pressure sensor.
Description of the Background Art
In recent years, semiconductor pressure sensors are used in various fields such as in vehicles. Some semiconductor pressure sensors are integrated with MOS (Metal Oxide Semiconductor) circuits. A semiconductor pressure sensor disclosed in Japanese National Patent Publication No. 2004-526299 (Patent Document 1) will be described as this type of semiconductor pressure sensor.
The semiconductor pressure sensor has a semiconductor substrate including the following defined regions: a region (MOS region) in which a MOS circuit is formed; and a region (pressure sensor region) in which a pressure sensor is formed. In the MOS region, a MOS circuit is formed including an n channel type MOS transistor and a p channel type MOS transistor. In the pressure sensor region, a capacitive type pressure sensor is formed. The capacitive type pressure sensor includes a fixed electrode and a movable electrode, and has a vacuum chamber provided between the fixed electrode and the movable electrode. The vacuum chamber is sealed by a sealing film. The pressure is measured by detecting a change in the distance between the movable electrode and the fixed electrode as a change in the capacitance value.
Meanwhile, for the movable electrode of such a pressure sensor, an anchor for supporting the movable electrode is preferably formed as disclosed in Japanese Patent Laying-Open No. 11-281509 (Patent Document 2), for example. With this, reliability of control for position of the movable electrode relative to the fixed electrode can be improved more.